In the past, the viscosity of a fluid has been measured utilizing a number of systems and techniques. For example, viscosity may be identified by measuring the force required to move a piston through a fluid, measuring the decay rate associated with a tuning fork excited within a fluid, measuring the time it takes a metal ball to roll down an incline within a fluid sample, or by measuring the time it takes a sample volume of fluid to exit through a constriction as it is pulled by gravitational forces.
However, many manners of determining viscosity generally require that the fluid sample be removed from the machine or other device that maintains the fluid for subsequent analysis. For example, oil used in an engine needs to be extracted and then separately analyzed on a testing bench to ascertain its viscosity. Such an endeavor generally requires that the machine be taken off-line or otherwise placed in an inoperable state so that the appropriate personnel can access the vehicle to extract the oil for testing. Unfortunately, the inoperability of the machine, results in a loss of productivity for those reliant on its operation. Thus, such techniques for assessing fluid viscosity are generally inefficient, and impose added operating costs, as the equipment utilizing the fluid to be analyzed must be taken out of service before testing of the fluid can be performed.
In addition, while many existing viscometers are capable of determining the viscosity of a fluid over various ranges of flow rates, most of these devices are not capable of accurately determining viscosity when fluid flow rates are low. As such, the operator or supervisor overseeing the operation of a machine or other equipment that utilizes low fluid flow rates is required to rely primarily on the performance specifications defined by the manufacturer of the fluid, which is generally undesirable when maintaining the operation of costly equipment that cannot readily be replaced.
There has recently been a trend toward utilizing debris analysis monitors, such as optical flow cell monitors, to analyze and detect debris that may be present in the lubricating fluid used by a machine. Such debris monitors facilitate the determination of a wear condition of the machine, and allow maintenance technicians to accurately identify when the fluid needs replacement and/or whether a particular operating component of the machine is in need of repair. However, such debris analysis monitors provide only data relating to the wear state of the machine, which maintains the fluid, and does not provide any information concerning the viscosity of the fluid. As such, operators of machines that employ the use of a flow cell are currently required to install another separate system in order to identify the viscosity of the fluid. Unfortunately, such viscosity measurement systems are costly, and tend to be bulky, making them potentially difficult to be installed in and about various machines.
The determination of a fluid's viscosity is beneficial in assessing whether the components of the fluid have been broken down or have degraded beyond a safe point. Furthermore, the determination of viscosity is beneficial in identifying the performance parameters or characterizing other parameters of the fluid so that the operation of a machine that utilizes the fluid can be monitored for potential adverse events.
Therefore, there is a need in the art for a viscometer system to derive fluid viscosity utilizing a flow cell with a calibrated constriction and a pressure sensor. Furthermore, there is a need for a viscometer system that can be retrofit, or otherwise added-on to the components of an existing flow cell to derive fluid viscosity. And, there is a need in the art for a viscometer system to derive fluid viscosity that is compact in size allowing the system to be incorporated with a machine whose fluid is being monitored. There is also a need in the art for a viscometer system to derive fluid viscosity over a wide viscosity and temperature range. Still yet there is a need for a viscometer system that can accurately derive the viscosity of a fluid having low flow rates.